MTK

In a pinch, I've used masking tape on the shaft to build up to 10mm diameter.

I have avoided the situation as much as possible though, by using APC props. They fit the shaft just right, as is. I've found thrust to be better and noise to be subdued..... using larger props on mine, 20+ inches diamteer and 10+ inches pitch.....BUT, weight is greateron the APC plastic props. Wood props are 70% the weight

Ken Cz

I found a piece of aluminum tubing about 6in long on Ebay with a 10.0 OD and a 8.0 ID. The fellow was overseas in Cyprus as I recall and I still got it in a week with no problem.
Just cut off the length you need, de-burr it, and you are on your way!

jdann

Hi Guys
I am running a GT 33 in a H9 Mustang (Mustang Sally) - perfect for it by the way - tremendous power. I have about 2 gallons through it and notice a clicking/clunking type sound when flipped backward just as it comes up on compression. I do not belive it was doing this before. It is running strong and I have flown it once, since noticing the sound, without issue. Connecting rod freeing up maybe? It does not do this when flipped forward through compression.
Any thoughts?

Ken Cz

I know OS says to use double the amount of Oil when mixing fuel for this engine but that seems a bit over the top as it may cause excessive fouling and carbon build-up.
The says to double whatever the Oil manufacturer recommends for their oil - Another words, if Pennzoil says 32-1 ratio and I should mix it up at 16-1??? Wow.
Sounds like overkill - what oil and mix ratio have you folks been using and with what results on new OS GT33's?

MTK

Nice plane.....I recall something similar with one of my 33's. Now after 40 gallons through it, I don't hear anything. Just smooth quiet output. Regarding oil content, I used 50:1 from the start, for break in and regular running. Never did change the oil BTW. The same mix from the start. Every 10 gallons or so I take it apart for cleaning but it hardly needs any. I use avgas so your milage may vary on maintenance

It takes a good 4-5 gallons for the engine to fully free up. Bearings and surfaces loosen up just great but the compression is as high today as when the engine was new.....I've said it before but worth repeating....arguably the "best" engine OS ever released

Ken Cz

MTK,
What Brand oil do you use at 50-1?

Seems like it has worked well for you so I will go the same way.

Ken

jdann

Thanks for that. I hate hearing clunking sounds from inside motors

MTK

Ken,
There are several fine oils out there. I use BelRay MC1 motorcycle racing synthetic but Redline I hear isexcellent, Stihl Ultra, Penzoil, several others. Choose one and stay with it
It is turning out that Avgas is burning super clean. Practically no carbon build up....every ten to fifteen gallons the plug needs a little cleaning of the lead in the gas. No biggIe.....

Beej

Hi,

Sorry if this is a dumb question. Just replacing my SAP180 with the GT33 in an Aeroworks Edge and I notice that the throttle spring is holding the carb open so the throttle pushrod has some work to do to open it and so needs quite a bit of stiffness and maybe not even suited to golden rod?. I have been using pull -pull cable on my larger planes with DA engines for throttle because the spring runs in the other direction and I like this set up. I there any way of reversing the current arrangement on the Gt33? It seems like a strange way to configure the engine/carb but maybe this is my mistake?

Thanks

Beej

MTK

Beej,

I haven't had a problem at all. I do move the spring into the arm hole to reduce tension. Actuation is the same as with glow, that is, push to open.

Just put the second GT into service. Same easy manners as the first. The first has 100+ hours on it and runs strong still.

vertical grimmace

My Feedback: (1)

So at this point, is this the best 30cc sized engine on the market? I have a DLE 30 (side exhaust) and feel it is the worst of their offerings. Shakes terribly, and others at my club experience the same thing. I will be in the market for engines in this size, would prefer rear exhaust, but I guess I can live with side if necessary. I am hoping the DLE 35R is better than the 30, but I am just looking for opinions.

MTK

One man's opinion....YES!! BUT I have not run all in the class, just enough to state my opinion with conviction

The qualifiers are as follows: most power (highest compression most likely), best reliability, ability to haul big props (the latest I am running on my piped 33 is an APC 20.5 x 10 PN), outstanding mid range response, outstanding mid range tork (very similar to a YS 175 on 30% nitro) simple field manners (after learning curve), well finished requiring no extra sealing, reed seating or anything you read about with others, and long life. Oh yeah, and one that wins many points with me, no screwey screws to install props

On the down side, the CDI is different and requires some learning initially; I had a tough time hand starting mine so I got a Sullivan Dynatron for it. Now it's hardly ever used. Takes a good 5 gallons to fully break in, except I use the same synthetic mix for break in as I do running, so YMMV here. My original copy had a factory defect so I only got 4 runs on mine initially before repairs. Hobby Services got the engine back in good shape except it took 4 weeks. Practically no maintenance since then, except for plug cleaning every 10 gallons. For my application, rear exhaust would be much much better, but that's just me.... I also would like to see a nose ring boss up front so that it's simple to install nose rings for soft mounted applications like mine......

Beej

Thanks Matt - your contributions to these forums is always high quality. I have installed the throttle with a nice stiff pushrod and all looks good - hopefully first start and in the air next week end. (BTW - I know you're on an eternal hunt for the best gas engine for pattern - have you seen the claimed prop data for the DA 35 on their facebook page? Seems out of this world... Still no sign of the engine on the market yet though..).

cheers,

Beej

MTK

Beej, Thanks

I don't ever look at Facebook pages. So, no, I have not seen any of their claims. Would you send a link please?

Stu26

I am thinking of getting the os33, how is the standard exhaust for noise? I do have a toni clark mini pipe for a zenoah 26 (It seems to be a zimmerman can), would that be ok on the os?

Roberto B.

MTK

Both are Hall sensors, and both engine types have magnets embedded for the sensor to , well, sense

Roberto B.

Thanks, Matt.

MTK

Don't mention it Roberto....The answer is incomplete tho. I would not use the RCxcl CDI on the OS 33. The firing programming is different and requires a much different Hall sensor position. If that is the intent, make sure you position the sensor at 28 degrees BTDC and it should work great on the OS GT33....

skillet92

Well I have the dle 3, (2) and a dle35 in a H9 Mustang. The 35 is much better than the 30 in power and vibration. I have a H9 30 P-47 that I am looking for an engine for. One of the recommended engines is an Evolution 40. Would this 33 be good for that plane? Gonna weight in the 18 pound range. I don't mind the side exhaust for this plane because I have plenty of room.

Roberto B.

I'm going to use the original CDI. I just need more sensors because I'm playing with some nose rings...

MTK

For what it's worth to anyone, a couple weeks ago I commissioned another OS GT33, except, since the model was already set-up for a DLE carb, I changed the carbie on the 33 to that of the DLE. These are about as close to the same parts as you can get without being identical; throat diameters are the same, pressure port locations are the same, throttle arm and choke arm locations are the same, and so on. Since the DLE carb was already set-up and needled, I tried it as is on the OS. It required no additional tweeking much to me surprise.

Point is the DLE35/DLE55 carbs are identical and either one fits the OS just great. There is a slight cost benefit to the DLE carbies tho, so beware

skillet92

Can anybody that has this engine tell me any thrust numbers. I am not as concerned with RPMs as I am with thrust. I am wanting to put this on a H9 30cc P-47 that will weight almost 18 pounds. Would like to have at least 18-20 pounds of thrust. The DLE 35 I have on my H9 150 Mustang has 19 pounds of thrust. I am sure that this one would have at least that if not more. thanks guys

Beej

Number from RC Sportflyer magazine review of OSGT33 are as follows (very highly recommended magazine and reviews BTW!)



RPM Static Thrust lb Pitch Speed Mph Sound Level dBA
APC 18X6W 9100 23.4 51.7 101.5
APC 18X8 8875 20.2 67.2 100.8
APC 18X10 8025 16.6 76.0 96.8
APC 18X12 7600 16.4 86.4 95.8
Mejzlik 19X8 7700 21.4 58.3 97.3
APC 19X11 6725 20.1 70.1 93.4
APC 20X8 7325 22.0 55.5 96.2
APC 20X10 6700 18.6 63.4 94.1

MTK

The RC Sprtflyer article that Beej showed was done with the 33 set-up stock. That is, hard mounted and with the included muffler,

There is quite a bit more performance that can be had from this engine if one was to run it on a tuned pipe. For example, I've run the engine on pipe and premium gas using a 20x10.5 PN APC prop, and got around 7800 rpm (TNC tach). I normally run avgas in my engines which drops rpm down to 74-7500 on the same APC prop. Thrust is around 24 lbs

Regarding noise, there is more quietness to be had by running the engine on a soft rubber isolation mount similar to a Hyde. That's what I use and get noise down to around 91-92 dB. To get an idea of how quiet that is, consider that when flying in a breezy day, the breeze practically drowns it out almost immediately after take off. Gas engines do not have to sound like chain saws to be effective.

And please, I know that tuned pipes don't fit every application. I am simply stating what's possible with this engine